Brake adjustment



20, 1940- G. 5. LANE BRAKE ADJUSTMENT Filed May 26, 1936 INVENTOR 625ml 5 W AME 3 ATTORNEi Patented Aug. 20, 1940 UNITED STATES PATENT OFFICE 1 Claim.

This invention relates to brakes and more particularly to self-adjusting vehicle braking systerns.-

In the accompanying drawing I have shown one embodiment of my invention with a view to illustrating the invention and its practical application and explaining the principle thereof, so 1 Referring first to Fig. 1, I have there shown a portion of a hydraulically operated braking system such as is now in common use on standard motor vehicles. The brake shoe I0 is a T section arcuate member having a facing ll thereon of a suitable friction material which is shaped and positioned so as to have a small uniform clearance from the rotating drum l2. In normal practice this clearance varies from about 0.020" to 0.005". The shoe I0 is moved into engagement with the drum I! by force applied to it from the piston of the brake operating motor I and this in turn is provided with fluid under pressure, e. g., from a pedal operated master cylinder and suitable piping connections, not shown herein, but which may, for example, be as shown in my prior applications, Serial Nos. 65,049, 73,703, and 77,225. Upon release of pressure from the motor M the shoe I0 is retracted to the released position as shown in Fig. 1 by the retracting spring IS. A spring l9 between the pistons I3 holds them against the shoes l0 when the brake system is in the released condition.

Thus far the construction is entirely according to standard practice and the brake shoe I0 is shown merely as representative of any type of 5 brake device which may be subject to wear, and

the brake operating parts H and 15 are representative of any brake operating and retracting devices, and particularly of a brake operating device which, like the hydraulic system, is capable of readjusting itself automatically when in the released condition to permit the full return of the pedal or other force applying means and thereby to permit the operating stroke to become effective immediately upon the braking element regardless of its released position.

A feeler or spacer 20 is used in my present invention, for example, as shown in Figs. 1 and '2. While a fixed stop is used it is adjustable by the snail cam 30. In this case an opening is made through the brake shoe adjacent the spiral ad- 5 justing cam 30 which, in'a present standard construction, forms the limiting stop for retraction of the brake shoe. A ratchet plate 3| is fixed to the back of the shoe l0 surrounding the opening through which the feelermember 20 is ex- 10 tended. This plate 3| is of spring metal and has a circular opening smaller in diameter than the diameter of the feeler 20 and has radial slits 32 forming spring fingers between them which engage the member 20 and hold it against the 15 pressure exerted by the spring l5.

Thus as the brake wears the pressure of the shoe l0 against the brake drum 12 will always bring the outer end of the member 20 substantially flush with the face of the lining II. The 20 member 20 is made of a length sufliciently less than the distance between the drum l2 and the fixed stop 30 to allow the desired clearance from the drum, e. g., 0.015", and thus each time the brake shoe I0 is retracted it is held with'the 25 face of the lining ll substantially 0.015" from the inner face of the drum l2, and regardless of wear, since the member 20 will always be pushed down to a position flush with the base of the lining. 30

In this case it is desirable to have the member 20 wear as little as possible and its material will be chosen with that in view.

In most cases, however, the expansion of the drum due to the frictional heat developed in 5 the braking operation can be compensated for by a corresponding expansion in the stop member 30 and the feeler 20. Thus if aluminum is used as the metal for this stop and the distance between its point of attachment and the point 4 of contact with the feeler 20 is properly related, taking into consideration the co-eficients of thermal expansion of the drum and of the stop member and the relative temperatures attained by the two members, the expansion of the aluminum may be made substantially to compensate for the expansion of the drum and such variations as occur in any normal operation may be absorbed as a slight increase or decrease in the clearance between the lining and the drum without substantially affecting the proper operation of the brake.

I claim:

A braking system having a braking element 55 10 tween the stop and brake drum being less than the entire distance therebetween measured along its length, and in which the feeler memberisof wearresisting relatively hard material, and the means for preventing its movement toward the drum is a resilient washer slit to form opposing fingers spaced end from end a distance less than the thickness of the feeler member, whereby said fingers act on the feeler member as a silent ratchet.

GEORGE S. LANE. 

